Process of electroplating



' a ndtliegarticle coated thereby."

UNITED STATES PATENT OFFICE.

TAKES S. GEOFF, OIKNEWPOBiil, RHODE ISLAND.

rnocnss or" ELnc'rnorLn'rme.

No Drawing.

To all whom it m concern:

Be it known that. I, lli Es S wGRoir-Qa 'citizen theflflnite'd ta'tes'f at.- Newport, Rhode Island, have invented iew and useful ,Improvemefits'in Processes: of Electroplatingof which the "following" is a spedificatiom' p v This invention relates to an improved proc or" fethod ofelectro-platingmetalhc bodiesas well asto the improyedieeating one "of the ob'ects' of the'prese1 1t inven tion is to tprovi e an improved method of metal sol'treated. v The protectlve coatings now t-io'ns in temperatures ,or

'- ressures: *flasks employed in tor edaes,

' in. the air forced tion and. a t the -same .ductility to permit. the

coating metallic bodies "wQth aiprimaryview of, preventing erosionor' oxidationfof the employed are hot efiicient because they 310 not afford thor-=-- oug'h protection: to the surfaces I especially whensaid surfaces are subjected to expansio n and contraction "dileto ariousyariw when" in thefonn of a container they are subjected to excessive 'It has beenldiscovered, particu ally in the' construction and use of air.

for. example} that -theFconde nsation of, moisture containe 7 into the a ir' flask under pressure condenses and subsequently; produces rust and corrosion on the iii'tenori ofthe fflask which in timeseriously..weakens the walls thereofi, This-objection is over come in the present; coatingthe interior of the flask with an alloy adapted'to preventfeorrosion or oxidatime. possess 'suflicient: expansionof ,the flask under a highpressure as well as; th'eex- .pansiori and contraction due to yariations in temperature.v v I A= further object is .to provide, an. im-

. proved 'method :for coating metallic bodies I A further object btovedcoafing ingsof absolute homogeneity and'free from and particularly steel which will'he rela'-= tively inexpensive .to perform bothfrom the financial point of iew as well as thatot is .to p e n 'forjmetallic bodies or ca'sor' starting pointsjfor corrosion.

rovl e lw ic bodies. which.-wil1 all .pillih lS furtherobject is to alloy .for; coating metal hard and a to dissolve it from the anode.

invention -by-.- ui bly d the ,fiuoborate solution Specification of Letters Patent. Patented D 28 1920 Applicationflled'Aug'ust 18,-1920. Serial-No. 404,475.

be hardeg and less corrodib le andmore pliable and elastic than any otlier heretofore attenIpted-. so "far as known art obvious and derstgod that 'there'are also involved. certain .otliei'" metals; V l Itmay ha e been attempted to coatr metal e ther by lead or t 11 but such methods would be iIIIPIiLQtlQflblQ-ill the present 'c'ase for the reason that y tin plating isnot slifiiciently pliable and elasticto Withstand the expansion and contractionof metals under conditions 'of pressure or temperaturebhanges.

f" The present inventlon uses substantially equali-iaarts 'of'lead and. tin which are used in-castingthe anode subsequently used. Tin

,jocciipies practlcally thesanie'position in the.

scale of electromotive forces of solution that d lead does. Thatis to say, it takes about the same electromdtive force to "deposit ti'n distinct ntethodsof corifmerciahap pl1cat1 on tor the prevention of corrosion 0t a lead'plating isnot sufficiently (from the acid solution) that it does lead, or

p Consequently a mixture of tin and lead will behave prac-. tlcally as one metaL- j Y The preferred in thod for preparing electrolyte for this process consists in using a lead fluoborate solution by dissolving dry white leadin fluoboric acid with a small '1 amount of glue or'other colloids," dissolved in Hot water. The anodes are thenimmersed in electrolyte and a sheet of steel is arranged insolution to act as a temporary cathode. The electrolysis is begun and continued until the concentration of the lead and tin in the electrolyte is. substantially equivalent to per- The ..bath' isthen ready-for the electrol centages of bothinetals used in the anodes. 10 i deposition of -the lead-tin coating whic s well-known manner by substituting. the article to be coated for the temporary cathode,

I Recent investigations performed in theusual have proven that 'v Satisfactory results than t ives much more e fluosil cate,' the deposit being more homogeneous and adhering better to the surface of the article or container to be coated.

As an example of the electrolyte used, it is stated that the following ingredients in the contents are employed: hydrofluoric acid 204 lbs., 'boric acid 90 lbs., white lead 120 lbs., glue 6 ounces, all of which are thoroughly mixed in water to provide a solution of approximately 120 gallons. /In making this solution, the boric acid is preferably dissolved in the hydrofluoric acid to which is added whit-e lead in the form of a thin paste in water until effervescence has ceased. Glue dissolved in a little warm water is then added and thoroughly mixed with the above solution.

The entire solution is then placed in a pitch lined tank with the lead-tin anode and a temporary steel cathode and the electrolysis started and continued until the proper proportion, that is, substantially 50% leadtin, is obtained. With the use of a substantial three-volt current, it has been found upon tests that the coat of the temporary cathode increases at the rate of about 3% of tin pereight hours until equilibrium of ingredients with the anode has been obtained. When this point arrives the temporary cathodeis removed and the article to be processed is substituted.

This process is vastly superior to what is known as the hot process of wiping or dipping and stripping in that the final coating is of absolute homogeneity and free from all points permitting the starting of corrosion.

' It is thus seen that the present invention provides a simple and practical process of coating metal and particularly air-containers and is adapted to accomplish, among others, all of the objects and advantages herein set forth.

What I claim is:

1. The herein described method of protecting metal against corrosion which consists of forming an anode of lead and tin, providing an electrolyte of lead fluoborate and a cathode of steel and operating the electrolysis until the lead and tin in the electrolyte is substantially equivalent to percentages of both metals used in the anodes.

2. The herein described method of protecting metals against corrosion which consists in electrolytically depositing a lead-tin coating thereon.

3. The herein described method of protecting metals against corrosion which consists in electrolytically depositing a lead-tin coating thereon, the electrolyte being formed in part from a lead fluoborate solution.

4. The herein described method of protecting metals against corrosion which consists in forming an electrolyte having substantially equivalent percentages of lead and tin and electrolytically depositing the leadtin coating upon the metal to be protected.

5. An air flask or other parts of a torpedo, having an electrolytically deposited coating of lead and tin.

6. A container for compressed air adapt ed to withstand expansion under heavy pressures or due to variation in temperature, having a pliable and elastic coating of lead and tin electrolytically deposited thereon for the protection of steel or other metals used which are subject to expansion and contraction.

Signed at Newport, Rhode Island, this 28th day of June, 1920.

JAMES s. GROFF. i 

